CA2316652C - Moisture insensitive electroluminescent phosphor - Google Patents
Moisture insensitive electroluminescent phosphor Download PDFInfo
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- CA2316652C CA2316652C CA2316652A CA2316652A CA2316652C CA 2316652 C CA2316652 C CA 2316652C CA 2316652 A CA2316652 A CA 2316652A CA 2316652 A CA2316652 A CA 2316652A CA 2316652 C CA2316652 C CA 2316652C
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/02—Use of particular materials as binders, particle coatings or suspension media therefor
- C09K11/025—Use of particular materials as binders, particle coatings or suspension media therefor non-luminescent particle coatings or suspension media
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
- C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
- C09K11/58—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing copper, silver or gold
- C09K11/582—Chalcogenides
- C09K11/584—Chalcogenides with zinc or cadmium
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B33/00—Electroluminescent light sources
- H05B33/12—Light sources with substantially two-dimensional radiating surfaces
- H05B33/14—Light sources with substantially two-dimensional radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S118/00—Coating apparatus
- Y10S118/05—Fluidized bed
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- Inorganic Chemistry (AREA)
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- Chemical Vapour Deposition (AREA)
Abstract
A phosphor particle has thereon a moisture resistant treatment of a metallic nitride. By moisture resistant is meant a condition allowing the phosphor particle to function in a humid atmosphere for a significantly longer period of time than an untreated particle.
The method of making such phosphors comprises the steps of introducing an inert gas into a reaction vessel; charging phosphor particles into the reaction vessel;
heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to moisture-proof the phosphor particles. The nitride treated phosphor particles produced by this method, which can include the deposition of a nitride coating on the particles, have excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%). By avoiding restrictive reactions the method and apparatus can be used to manufacture commercial quantities of coated phosphors.
The method of making such phosphors comprises the steps of introducing an inert gas into a reaction vessel; charging phosphor particles into the reaction vessel;
heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to moisture-proof the phosphor particles. The nitride treated phosphor particles produced by this method, which can include the deposition of a nitride coating on the particles, have excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%). By avoiding restrictive reactions the method and apparatus can be used to manufacture commercial quantities of coated phosphors.
Description
MOISTURE INSENSITIVE ELECTROLUMINESCENT PHOSPHOR
TECHNICAL FIELD
This invention relates to electroluminescent phosphors and more particularly to electroluminescent phosphors that have been treated to be moisture resistant.
More particularly, this invention relates to electroluminescent phosphors having greatly reduced moisture absorption and greatly increased life and efficacy.
BACKGROUND ART
Treated phosphors are known from U.S. Patent Nos. 4,585,673; 4,825,124;
5,080,928;
5,118,529; 5,156,885; 5,220,243; 5,244,750; and 5,418,062. It is known from some of the just-mentioned patents that a coating precursor and oxygen can be used to apply a protective coating. See, for example, U.S. Patent Nos. 5,244,750 and 4,585,673. The treatment processes in several of the others of these patents employ chemical vapour deposition to apply a protective coating by hydrolysis. It also has been reported that chemical vapour deposition, at atmospheric pressure, can be used to deposit thin films of aluminum nitride coatings from hexakis(dimethylamido)dialuminum and anhydrous ammonia precursors upon silicon, vitreous carbon and glass substrates. See, for example, "atmospheric pressure chemical vapour deposition of aluminum nitride films at 200-250 C", Gordon, et al., Journal Material Resources, Vol. 6, No. 1, Jan. 1991; and "Chemical vapour deposition of aluminum nitride thin films", Gordon, et al., Journal Material Resources, Vol.
7, No. 7, Jul.
1992. See, also, U.S. Patent Nos. 5,139,825 and 5,178,911, Gordon, which also disclose transition metal nitrides and other metallic nitrides such as gallium and tin, respectively.
U.S. Patent No. 5,856,009 discloses a high temperature process (i.e., 300 to 700 C) for applying a silicon nitride coating over a previously applied heat resistant coating on phosphor particles. U.S. Patent application S.N. 09/175,787, filed 10/20/98 and issued as U.S. Patent No. 6,064,150, discloses a nitride coating process using a highly reactive hexakis(dimethylamido)dialuminum that has been difficult to scale up to commercial quantities. It would be an advance in the art to provide a process for providing moisture resistant electroluminescent phosphors. It would be a further advance if that process operated in the absence of water or water vapour. It would be a further advance in the art to increase the efficacy and the life of such phosphors manufactured by such a process. It would be still further advance in the art to provide a process that did not rely upon oxygen.
It would be a still further advance in the art to provide an electroluminescent phosphor with a non-oxide coating such, for example, as a metallic nitride coating that is applied directly to the phosphor particles at a low temperature, i.e., about 100 C so that the phosphor performance is not degraded. It would be a still further advance in the art to provide a process employing highly reactive materials that can yield commercial quantities of coated phosphor.
DISCLOSURE OF INVENTION
It is, therefore, desirable to obviate the disadvantages of the prior art.
It is also desirable to enhance the operation of moisture-resistant phosphors.
It is desirable to provide a method for providing moisture resistant phosphors that does not employ water or water vapour, or oxygen.
It is further desirable to provide a method and apparatus for providing commercial quantities of nitride coated phosphors which method and apparatus employ highly reactive materials.
There is disclosed a phosphor particle having thereon a coating of a metallic nitride. The coating may be conformal to the particle surface. By conformal is meant a coating that follows the surface contours of the individual particles.
There is also disclosed a process of preparing moisture resistant particles of electroluminescent phosphor, comprising the steps of. introducing an inert gas into a reaction vessel that is charged with phosphor particles; heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to make the phosphor particles moisture resistant. For example, the reaction vessel may have a porous disk at one end thereof and the nitride precursor may be introduced into the reaction vessel so that it does not pass through the disk.
TECHNICAL FIELD
This invention relates to electroluminescent phosphors and more particularly to electroluminescent phosphors that have been treated to be moisture resistant.
More particularly, this invention relates to electroluminescent phosphors having greatly reduced moisture absorption and greatly increased life and efficacy.
BACKGROUND ART
Treated phosphors are known from U.S. Patent Nos. 4,585,673; 4,825,124;
5,080,928;
5,118,529; 5,156,885; 5,220,243; 5,244,750; and 5,418,062. It is known from some of the just-mentioned patents that a coating precursor and oxygen can be used to apply a protective coating. See, for example, U.S. Patent Nos. 5,244,750 and 4,585,673. The treatment processes in several of the others of these patents employ chemical vapour deposition to apply a protective coating by hydrolysis. It also has been reported that chemical vapour deposition, at atmospheric pressure, can be used to deposit thin films of aluminum nitride coatings from hexakis(dimethylamido)dialuminum and anhydrous ammonia precursors upon silicon, vitreous carbon and glass substrates. See, for example, "atmospheric pressure chemical vapour deposition of aluminum nitride films at 200-250 C", Gordon, et al., Journal Material Resources, Vol. 6, No. 1, Jan. 1991; and "Chemical vapour deposition of aluminum nitride thin films", Gordon, et al., Journal Material Resources, Vol.
7, No. 7, Jul.
1992. See, also, U.S. Patent Nos. 5,139,825 and 5,178,911, Gordon, which also disclose transition metal nitrides and other metallic nitrides such as gallium and tin, respectively.
U.S. Patent No. 5,856,009 discloses a high temperature process (i.e., 300 to 700 C) for applying a silicon nitride coating over a previously applied heat resistant coating on phosphor particles. U.S. Patent application S.N. 09/175,787, filed 10/20/98 and issued as U.S. Patent No. 6,064,150, discloses a nitride coating process using a highly reactive hexakis(dimethylamido)dialuminum that has been difficult to scale up to commercial quantities. It would be an advance in the art to provide a process for providing moisture resistant electroluminescent phosphors. It would be a further advance if that process operated in the absence of water or water vapour. It would be a further advance in the art to increase the efficacy and the life of such phosphors manufactured by such a process. It would be still further advance in the art to provide a process that did not rely upon oxygen.
It would be a still further advance in the art to provide an electroluminescent phosphor with a non-oxide coating such, for example, as a metallic nitride coating that is applied directly to the phosphor particles at a low temperature, i.e., about 100 C so that the phosphor performance is not degraded. It would be a still further advance in the art to provide a process employing highly reactive materials that can yield commercial quantities of coated phosphor.
DISCLOSURE OF INVENTION
It is, therefore, desirable to obviate the disadvantages of the prior art.
It is also desirable to enhance the operation of moisture-resistant phosphors.
It is desirable to provide a method for providing moisture resistant phosphors that does not employ water or water vapour, or oxygen.
It is further desirable to provide a method and apparatus for providing commercial quantities of nitride coated phosphors which method and apparatus employ highly reactive materials.
There is disclosed a phosphor particle having thereon a coating of a metallic nitride. The coating may be conformal to the particle surface. By conformal is meant a coating that follows the surface contours of the individual particles.
There is also disclosed a process of preparing moisture resistant particles of electroluminescent phosphor, comprising the steps of. introducing an inert gas into a reaction vessel that is charged with phosphor particles; heating the reaction vessel to a reaction temperature; introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to make the phosphor particles moisture resistant. For example, the reaction vessel may have a porous disk at one end thereof and the nitride precursor may be introduced into the reaction vessel so that it does not pass through the disk.
There is further disclosed a method of making moisture-resistant phosphors which comprises the steps of introducing an inert gas into a reaction vessel;
charging phosphor particles into the reaction vessel; heating the reaction vessel to a reaction temperature;
introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to coat the phosphor particles.
In accordance with an aspect of the present invention, there is provided a process of preparing moisture resistant particles of electroluminescent phosphor, comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles and has a porous disk at one end thereof; heating said reaction vessel to a reaction temperature;
introducing a nitride precursor into said reaction vessel such that said nitride precursor does not pass through said disk; introducing a co-reactant into said reaction vessel; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
In accordance with another aspect of the present invention, there is provided an apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising a reaction vessel sized to accommodate the commercial quantities of the phosphor, the reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom; at least a first supply of an inert gas for initially fluidizing the phosphor, the inert gas being introduced into the vessel through the disk; a supply of nitride coating precursor; a supply of a carrier for entraining the precursor;
a supply of a co-reactant, the co-reactant being delivered to the vessel through the disk; and a delivery means for introducing entrained nitride coating precursor into the vessel through the second end.
In accordance with another aspect of the present invention, there is provided an apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising a reaction vessel sized to accommodate the commercial quantities of the phosphor, the reaction vessel having a first end containing a porous, gas 4a dispersing disk and a second end spaced therefrom; at least a first supply of an inert gas in fluid communication with the disk for initially fluidizing the phosphor; a supply of a nitride coating precursor; a supply of a carrier in fluid communication with the supply of nitride coating precursor for entraining the precursor thereby forming an entrained coating precursor; a supply of a co-reactant in fluid communication with the disk such that the co-reactant flows therethrough; and a delivery means in fluid communication with the supply of carrier and the supply of nitride coating precursor for providing the entrained coating precursor which enters the vessel through the second end.
In accordance with another aspect of the present invention, there is provided a process of preparing moisture resistant particles of electroluminescent phosphor, comprising introducing an inert gas into a reaction vessel that is charged with phosphor particles;
heating the reaction vessel to a reaction temperature; introducing a co-reactant into a first end of the reaction vessel through a porous gas dispersing disk; introducing a nitride precursor into the reaction vessel at a second end of the reaction vessel so that it does not pass through the gas dispersing disk to avoid restrictive reactions; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to make the phosphor particles moisture resistant.
In accordance with another aspect of the present invention, there is provided an apparatus for coating phosphor particles with nitride, comprising a reaction vessel defining a reaction zone to be charged with phosphor particles; a porous distributor disposed adjacent the reaction zone for dispersing a fluid into the reaction zone, a supply of an inert gas, in fluid communication with the reaction zone through the porous distributor; a supply of a nitride precursor, in fluid communication with the reaction zone without passing through the porous distributor; and a supply of a co-reactant, in fluid communication with the reaction zone.
In accordance with another aspect of the present invention, there is provided a process of coating phosphor particles with nitride, comprising dispersing an inert gas into a heated reaction zone through a porous distributor adjacent the reaction zone, to fluidize phosphor particles in the reaction zone; supplying a nitride precursor to the reaction zone without 4b passing through the porous distributor; and supplying a co-reactant to the reaction zone, so that the co-reactant reacts with the nitride precursor in the reaction zone to form coating on the fluidized phosphor particles.
Sample nitrided phosphor particles produced by this method had excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%) and can be made in viable commercial quantities, such as 50 kg batches.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagrammatic view of a prior art process for coating the phosphors; and Fig. 2 is a diagrammatic view of the process of the invention.
1 o BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
In a prior art embodiment of the invention shown in Fig. 1, the coating reaction was carried out in a gas-fluidized bed reaction vessel that comprised a one inch O.D.
(2.54 cm) glass tube 10 with a coarse porosity, fitted glass disk 12 as the gas distributor and surrounded by a heater 30 for maintaining reactor temperature. The phosphor 16 employed was a Type 723 electroluminescent phosphor (ZnS:Cu) available from Osram Sylvania Inc., Towanda PA and the phosphor was fluidized by the injection of an inert 5 gas such as nitrogen from a supply 18. The nitride coatings (which can contain amounts of hydrogen as well as the aluminum nitride) were formed via the reaction of anhydrous ammonia with hexakis(dimethylamido)dialuminum (A12(N(CH3)2)6). However, there is no reason to believe that other organo-metallic nitrides would not work as well, particularly, for example those containing gallium or tin. The aluminum nitride precursor was obtained from Strem Chemicals, Newburyport, MA, and contained within a stainless steel bubbler. The bubbler was maintained at 100 C and the precursor was transported to the reaction vessel by a carrier of purified nitrogen from supply 22. The precursor-entrained nitrogen was flowed upwards through the fitted glass distributor 12 through lines that were maintained 20 to 30 C above the temperature of the bubbler.
The anhydrous ammonia co-reactant 24, which was obtained from Matheson Chemicals, Gloucester, MA, was passed through a Unit mass flow controller 26 prior to entering the fluidized bed via a central glass tube 27 having a fritted glass tip 28. The anhydrous ammonia was diluted with purified nitrogen prior to entering the bed.
Additionally, the nitrogen carrier was purified by passing through a Centorr purifier followed by a Matheson Nanochem gas purifier. The ammonia, also, was passed through a Nanochem purifier.
The gas handling system was constructed from stainless steel tubing and fittings. Glass-to-metal seals were employed between the glass reactor parts and the gas lines.
This process worked well in the apparatus described for small quantities of phosphor, i.e., in the range of 40 grams or so. However, problems arose with the attempt to scale up production to commercial quantities in the kilogram range.
The problem has been identified as stemming from the reactivity of the nitride precursor, in this case the hexakis(dimethylamido)dialuminum. This material reacts with the coarse porosity, fitted glass disk, plating nitrides on the sides of the pores therein. This is particularly true at the elevated temperatures of the reaction vessel, which are in the neighborhood of 150 to 225 T. In very short order the pores of the disk are plugged, stopping the desired reaction of nitride coating on the suspended phosphor particles.
The solution to this problem is presented in the apparatus and method illustrated in Fig.
2. Therein, a reaction vessel 10a, which can be a stainless steel vessel having a diameter greater than 10 inches and being surrounded by a suitable heater 30a to bring the reaction vessel to a coating temperature between 150 and 225 C, has the coating precursor introduced into the vessel in a manner to avoid restrictive reactions. In the embodiment illustrated this is accomplished by entraining the precursor with nitrogen from supply 22a and feeding the entrained precursor from the top of the reaction vessel 10a through tube 32, which is open for its entire length and is not provided with a fritted glass tip. The co-reactant, in this case diluted anhydrous ammonia, can be fed from the bottom of vessel I Oa and passed through the porous glass disk 12a. The initial supply of inert gas, which can also be nitrogen and which is used for initially fluidizing the phosphor particles, can also be fed from the bottom of vessel I Oa, through disk 12a.
Thus, by feeding the nitride coating precursor in a manner to avoid restrictive reactions, nitride coated phosphors are prepared in commercial quantities in an economic system.
While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
charging phosphor particles into the reaction vessel; heating the reaction vessel to a reaction temperature;
introducing a nitride coating precursor into the reaction vessel in a manner to avoid restrictive reactions; introducing a co-reactant into the reaction vessel; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to coat the phosphor particles.
In accordance with an aspect of the present invention, there is provided a process of preparing moisture resistant particles of electroluminescent phosphor, comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles and has a porous disk at one end thereof; heating said reaction vessel to a reaction temperature;
introducing a nitride precursor into said reaction vessel such that said nitride precursor does not pass through said disk; introducing a co-reactant into said reaction vessel; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
In accordance with another aspect of the present invention, there is provided an apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising a reaction vessel sized to accommodate the commercial quantities of the phosphor, the reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom; at least a first supply of an inert gas for initially fluidizing the phosphor, the inert gas being introduced into the vessel through the disk; a supply of nitride coating precursor; a supply of a carrier for entraining the precursor;
a supply of a co-reactant, the co-reactant being delivered to the vessel through the disk; and a delivery means for introducing entrained nitride coating precursor into the vessel through the second end.
In accordance with another aspect of the present invention, there is provided an apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising a reaction vessel sized to accommodate the commercial quantities of the phosphor, the reaction vessel having a first end containing a porous, gas 4a dispersing disk and a second end spaced therefrom; at least a first supply of an inert gas in fluid communication with the disk for initially fluidizing the phosphor; a supply of a nitride coating precursor; a supply of a carrier in fluid communication with the supply of nitride coating precursor for entraining the precursor thereby forming an entrained coating precursor; a supply of a co-reactant in fluid communication with the disk such that the co-reactant flows therethrough; and a delivery means in fluid communication with the supply of carrier and the supply of nitride coating precursor for providing the entrained coating precursor which enters the vessel through the second end.
In accordance with another aspect of the present invention, there is provided a process of preparing moisture resistant particles of electroluminescent phosphor, comprising introducing an inert gas into a reaction vessel that is charged with phosphor particles;
heating the reaction vessel to a reaction temperature; introducing a co-reactant into a first end of the reaction vessel through a porous gas dispersing disk; introducing a nitride precursor into the reaction vessel at a second end of the reaction vessel so that it does not pass through the gas dispersing disk to avoid restrictive reactions; and maintaining the inert gas flow, co-reactant flow and precursor supply for a time sufficient to make the phosphor particles moisture resistant.
In accordance with another aspect of the present invention, there is provided an apparatus for coating phosphor particles with nitride, comprising a reaction vessel defining a reaction zone to be charged with phosphor particles; a porous distributor disposed adjacent the reaction zone for dispersing a fluid into the reaction zone, a supply of an inert gas, in fluid communication with the reaction zone through the porous distributor; a supply of a nitride precursor, in fluid communication with the reaction zone without passing through the porous distributor; and a supply of a co-reactant, in fluid communication with the reaction zone.
In accordance with another aspect of the present invention, there is provided a process of coating phosphor particles with nitride, comprising dispersing an inert gas into a heated reaction zone through a porous distributor adjacent the reaction zone, to fluidize phosphor particles in the reaction zone; supplying a nitride precursor to the reaction zone without 4b passing through the porous distributor; and supplying a co-reactant to the reaction zone, so that the co-reactant reacts with the nitride precursor in the reaction zone to form coating on the fluidized phosphor particles.
Sample nitrided phosphor particles produced by this method had excellent efficacy ratings and strong luminance values in lamps after 100 hours use in high humidity (i.e., >95%) and can be made in viable commercial quantities, such as 50 kg batches.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a diagrammatic view of a prior art process for coating the phosphors; and Fig. 2 is a diagrammatic view of the process of the invention.
1 o BEST MODE FOR CARRYING OUT THE INVENTION
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims taken in conjunction with the above-described drawings.
In a prior art embodiment of the invention shown in Fig. 1, the coating reaction was carried out in a gas-fluidized bed reaction vessel that comprised a one inch O.D.
(2.54 cm) glass tube 10 with a coarse porosity, fitted glass disk 12 as the gas distributor and surrounded by a heater 30 for maintaining reactor temperature. The phosphor 16 employed was a Type 723 electroluminescent phosphor (ZnS:Cu) available from Osram Sylvania Inc., Towanda PA and the phosphor was fluidized by the injection of an inert 5 gas such as nitrogen from a supply 18. The nitride coatings (which can contain amounts of hydrogen as well as the aluminum nitride) were formed via the reaction of anhydrous ammonia with hexakis(dimethylamido)dialuminum (A12(N(CH3)2)6). However, there is no reason to believe that other organo-metallic nitrides would not work as well, particularly, for example those containing gallium or tin. The aluminum nitride precursor was obtained from Strem Chemicals, Newburyport, MA, and contained within a stainless steel bubbler. The bubbler was maintained at 100 C and the precursor was transported to the reaction vessel by a carrier of purified nitrogen from supply 22. The precursor-entrained nitrogen was flowed upwards through the fitted glass distributor 12 through lines that were maintained 20 to 30 C above the temperature of the bubbler.
The anhydrous ammonia co-reactant 24, which was obtained from Matheson Chemicals, Gloucester, MA, was passed through a Unit mass flow controller 26 prior to entering the fluidized bed via a central glass tube 27 having a fritted glass tip 28. The anhydrous ammonia was diluted with purified nitrogen prior to entering the bed.
Additionally, the nitrogen carrier was purified by passing through a Centorr purifier followed by a Matheson Nanochem gas purifier. The ammonia, also, was passed through a Nanochem purifier.
The gas handling system was constructed from stainless steel tubing and fittings. Glass-to-metal seals were employed between the glass reactor parts and the gas lines.
This process worked well in the apparatus described for small quantities of phosphor, i.e., in the range of 40 grams or so. However, problems arose with the attempt to scale up production to commercial quantities in the kilogram range.
The problem has been identified as stemming from the reactivity of the nitride precursor, in this case the hexakis(dimethylamido)dialuminum. This material reacts with the coarse porosity, fitted glass disk, plating nitrides on the sides of the pores therein. This is particularly true at the elevated temperatures of the reaction vessel, which are in the neighborhood of 150 to 225 T. In very short order the pores of the disk are plugged, stopping the desired reaction of nitride coating on the suspended phosphor particles.
The solution to this problem is presented in the apparatus and method illustrated in Fig.
2. Therein, a reaction vessel 10a, which can be a stainless steel vessel having a diameter greater than 10 inches and being surrounded by a suitable heater 30a to bring the reaction vessel to a coating temperature between 150 and 225 C, has the coating precursor introduced into the vessel in a manner to avoid restrictive reactions. In the embodiment illustrated this is accomplished by entraining the precursor with nitrogen from supply 22a and feeding the entrained precursor from the top of the reaction vessel 10a through tube 32, which is open for its entire length and is not provided with a fritted glass tip. The co-reactant, in this case diluted anhydrous ammonia, can be fed from the bottom of vessel I Oa and passed through the porous glass disk 12a. The initial supply of inert gas, which can also be nitrogen and which is used for initially fluidizing the phosphor particles, can also be fed from the bottom of vessel I Oa, through disk 12a.
Thus, by feeding the nitride coating precursor in a manner to avoid restrictive reactions, nitride coated phosphors are prepared in commercial quantities in an economic system.
While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
Claims (11)
1. A process of preparing moisture resistant particles of electroluminescent phosphor, comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles and has a porous disk at one end thereof;
heating said reaction vessel to a reaction temperature;
introducing a nitride precursor into said reaction vessel such that said nitride precursor does not pass through said disk;
introducing a co-reactant into said reaction vessel; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
introducing an inert gas into a reaction vessel that is charged with phosphor particles and has a porous disk at one end thereof;
heating said reaction vessel to a reaction temperature;
introducing a nitride precursor into said reaction vessel such that said nitride precursor does not pass through said disk;
introducing a co-reactant into said reaction vessel; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
2. An apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising:
a reaction vessel sized to accommodate said commercial quantities of said phosphor, said reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom;
at least a first supply of an inert gas for initially fluidizing said phosphor, said inert gas being introduced into said vessel through said disk;
a supply of nitride coating precursor;
a supply of a carrier for entraining said precursor;
a supply of a co-reactant, said co-reactant being delivered to said vessel through said disk; and a delivery means for introducing entrained nitride coating precursor into said vessel through said second end.
a reaction vessel sized to accommodate said commercial quantities of said phosphor, said reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom;
at least a first supply of an inert gas for initially fluidizing said phosphor, said inert gas being introduced into said vessel through said disk;
a supply of nitride coating precursor;
a supply of a carrier for entraining said precursor;
a supply of a co-reactant, said co-reactant being delivered to said vessel through said disk; and a delivery means for introducing entrained nitride coating precursor into said vessel through said second end.
3. An apparatus for manufacturing commercial quantities of nitride coated electroluminescent phosphors via a fluidized bed, comprising:
a reaction vessel sized to accommodate said commercial quantities of said phosphor, said reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom;
at least a first supply of an inert gas in fluid communication with said disk for initially fluidizing said phosphor;
a supply of a nitride coating precursor;
a supply of a carrier in fluid communication with said supply of said nitride coating precursor for entraining said precursor thereby forming an entrained coating precursor;
a supply of a co-reactant in fluid communication with said disk such that said co-reactant flows therethrough; and a delivery means in fluid communication with said supply of said carrier and said supply of said nitride coating precursor for providing said entrained coating precursor which enters said vessel through said second end.
a reaction vessel sized to accommodate said commercial quantities of said phosphor, said reaction vessel having a first end containing a porous, gas dispersing disk and a second end spaced therefrom;
at least a first supply of an inert gas in fluid communication with said disk for initially fluidizing said phosphor;
a supply of a nitride coating precursor;
a supply of a carrier in fluid communication with said supply of said nitride coating precursor for entraining said precursor thereby forming an entrained coating precursor;
a supply of a co-reactant in fluid communication with said disk such that said co-reactant flows therethrough; and a delivery means in fluid communication with said supply of said carrier and said supply of said nitride coating precursor for providing said entrained coating precursor which enters said vessel through said second end.
4. A process of preparing moisture resistant particles of electroluminescent phosphor, comprising:
introducing an inert gas into a reaction vessel that is charged with phosphor particles;
heating said reaction vessel to a reaction temperature;
introducing a co-reactant into a first end of the reaction vessel through a porous gas dispersing disk;
introducing a nitride precursor into said reaction vessel at a second end of the reaction vessel so that it does not pass through the gas dispersing disk to avoid restrictive reactions; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
introducing an inert gas into a reaction vessel that is charged with phosphor particles;
heating said reaction vessel to a reaction temperature;
introducing a co-reactant into a first end of the reaction vessel through a porous gas dispersing disk;
introducing a nitride precursor into said reaction vessel at a second end of the reaction vessel so that it does not pass through the gas dispersing disk to avoid restrictive reactions; and maintaining flows of said inert gas, co-reactant and precursor for a time sufficient to make said phosphor particles moisture resistant.
5. An apparatus for coating phosphor particles with nitride, comprising:
a reaction vessel defining a reaction zone to be charged with phosphor particles;
a porous distributor disposed adjacent said reaction zone for dispersing a fluid into said reaction zone, a supply of an inert gas, in fluid communication with said reaction zone through said porous distributor;
a supply of a nitride precursor, in fluid communication with said reaction zone without passing through said porous distributor; and a supply of a co-reactant, in fluid communication with said reaction zone.
a reaction vessel defining a reaction zone to be charged with phosphor particles;
a porous distributor disposed adjacent said reaction zone for dispersing a fluid into said reaction zone, a supply of an inert gas, in fluid communication with said reaction zone through said porous distributor;
a supply of a nitride precursor, in fluid communication with said reaction zone without passing through said porous distributor; and a supply of a co-reactant, in fluid communication with said reaction zone.
6. The apparatus of claim 5, wherein said supply of said co-reactant is in fluid communication with said reaction zone through said porous distributor.
7. The apparatus of claim 5 or claim 6, wherein said porous distributor comprises a porous disk.
8. The apparatus of any one of claims 5 to 7, comprising a supply of a carrier, in fluid communication with said supply of said nitride precursor for carrying said nitride precursor to said reaction zone.
9. A process of coating phosphor particles with nitride, comprising:
dispersing an inert gas into a heated reaction zone through a porous distributor adjacent said reaction zone, to fluidize phosphor particles in said reaction zone;
supplying a nitride precursor to said reaction zone without passing through said porous distributor; and supplying a co-reactant to said reaction zone, so that said co-reactant reacts with said nitride precursor in said reaction zone to form coating on said fluidized phosphor particles.
dispersing an inert gas into a heated reaction zone through a porous distributor adjacent said reaction zone, to fluidize phosphor particles in said reaction zone;
supplying a nitride precursor to said reaction zone without passing through said porous distributor; and supplying a co-reactant to said reaction zone, so that said co-reactant reacts with said nitride precursor in said reaction zone to form coating on said fluidized phosphor particles.
10. The process of claim 9, wherein said co-reactant is supplied to said reaction zone through said porous distributor.
11. The process of claim 9 or claim 10, wherein said porous distributor comprises a porous disk.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/406,359 US6171650B1 (en) | 1999-09-28 | 1999-09-28 | Moisture insensitive electroluminescent phosphor |
| US09/406,359 | 1999-09-28 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2316652A1 CA2316652A1 (en) | 2001-03-28 |
| CA2316652C true CA2316652C (en) | 2011-03-15 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2316652A Expired - Fee Related CA2316652C (en) | 1999-09-28 | 2000-08-24 | Moisture insensitive electroluminescent phosphor |
Country Status (9)
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|---|---|
| US (2) | US6171650B1 (en) |
| EP (1) | EP1088874B1 (en) |
| JP (1) | JP4443748B2 (en) |
| CN (1) | CN1198898C (en) |
| AT (1) | ATE262570T1 (en) |
| CA (1) | CA2316652C (en) |
| DE (1) | DE60009224T2 (en) |
| HU (1) | HU226916B1 (en) |
| RU (1) | RU2247761C2 (en) |
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| US6064150A (en) * | 1998-01-12 | 2000-05-16 | Osram Sylvania Inc. | Nitride coated particle and composition of matter comprised of such particles |
| JP3829464B2 (en) * | 1998-03-25 | 2006-10-04 | 双葉電子工業株式会社 | Phosphor and method for producing phosphor |
| US6733826B2 (en) * | 2000-12-18 | 2004-05-11 | Osram Sylvania Inc. | Method and apparatus for coating electroluminescent phosphors |
| US6569357B2 (en) * | 2000-12-18 | 2003-05-27 | Osram Sylvania Inc. | Method of making electroluminescent phosphor |
| CN102822313B (en) | 2010-03-31 | 2014-11-26 | 积水化学工业株式会社 | Surface-treated fluorescent bodies and process for production of surface-treated fluorescent bodies |
| US8791488B2 (en) | 2010-08-04 | 2014-07-29 | Sekisui Chemical Co., Ltd. | Surface-treated fluorescent material and process for producing surface-treated fluorescent material |
| EP2719753B1 (en) * | 2012-10-11 | 2015-02-25 | Friedrich-Alexander-Universität Erlangen-Nürnberg | Reactor with electroluminescence particles in the reaction medium |
| US10174242B1 (en) | 2018-05-17 | 2019-01-08 | Eie Materials, Inc. | Coated thioaluminate phosphor particles |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL7403205A (en) * | 1974-03-11 | 1975-09-15 | Philips Nv | METHOD OF MANUFACTURE OF A CATHODE RAY TUBE FOR DISPLAYING COLORED IMAGES AND CATHOD RAY TUBE MADE IN ACCORDANCE WITH THIS PROCESS. |
| US4173660A (en) * | 1977-07-27 | 1979-11-06 | The United States Of America As Represented By The United States Department Of Energy | Method of preparing a thermoluminescent phosphor |
| US4121010A (en) * | 1977-07-27 | 1978-10-17 | The United States Of America As Represented By The United States Department Of Energy | Thermoluminescent phosphor |
| US4540914A (en) * | 1982-12-17 | 1985-09-10 | Lockheed Missiles & Space Company, Inc. | Absorbing graded nitride film for high contrast display devices |
| JP2677818B2 (en) * | 1987-08-17 | 1997-11-17 | コニカ株式会社 | Radiation image conversion panel |
| US5071590A (en) * | 1990-11-13 | 1991-12-10 | Gte Products Corporation | Method for increasing the cohesiveness of powders in fluid beds |
| US5126166A (en) * | 1990-12-21 | 1992-06-30 | Gte Products Corporation | Method of reducing the degradation of the red phosphor, Y203:EU, in water base lamp suspensions |
| JPH11166180A (en) * | 1997-12-03 | 1999-06-22 | Futaba Corp | Phosphor and production thereof |
| US6064150A (en) * | 1998-01-12 | 2000-05-16 | Osram Sylvania Inc. | Nitride coated particle and composition of matter comprised of such particles |
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1999
- 1999-09-28 US US09/406,359 patent/US6171650B1/en not_active Expired - Lifetime
-
2000
- 2000-08-24 CA CA2316652A patent/CA2316652C/en not_active Expired - Fee Related
- 2000-09-27 RU RU2000124617/15A patent/RU2247761C2/en not_active IP Right Cessation
- 2000-09-27 JP JP2000293744A patent/JP4443748B2/en not_active Expired - Fee Related
- 2000-09-27 HU HU0003780A patent/HU226916B1/en not_active IP Right Cessation
- 2000-09-28 DE DE60009224T patent/DE60009224T2/en not_active Expired - Lifetime
- 2000-09-28 CN CNB001292587A patent/CN1198898C/en not_active Expired - Fee Related
- 2000-09-28 EP EP00121150A patent/EP1088874B1/en not_active Expired - Lifetime
- 2000-09-28 AT AT00121150T patent/ATE262570T1/en not_active IP Right Cessation
- 2000-10-05 US US09/685,841 patent/US6364951B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| DE60009224D1 (en) | 2004-04-29 |
| EP1088874A1 (en) | 2001-04-04 |
| JP4443748B2 (en) | 2010-03-31 |
| HU0003780D0 (en) | 2000-09-27 |
| HU226916B1 (en) | 2010-03-01 |
| RU2247761C2 (en) | 2005-03-10 |
| HUP0003780A3 (en) | 2002-02-28 |
| ATE262570T1 (en) | 2004-04-15 |
| CA2316652A1 (en) | 2001-03-28 |
| DE60009224T2 (en) | 2004-08-19 |
| CN1198898C (en) | 2005-04-27 |
| US6171650B1 (en) | 2001-01-09 |
| US6364951B1 (en) | 2002-04-02 |
| HUP0003780A2 (en) | 2001-09-28 |
| EP1088874B1 (en) | 2004-03-24 |
| JP2001139941A (en) | 2001-05-22 |
| CN1289816A (en) | 2001-04-04 |
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